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Complex patterns of inheritance Chapter 13. Pedigrees. Tracking Family History. Pedigrees. A chart that shows multiple family generations and relationships to track the inheritance of genetic traits. Pedigrees. Can be used to determine genotypes of family members . - PowerPoint PPT Presentation
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Tracking Family History
A chart that shows multiple family generations and relationships to track the inheritance of genetic traits.
Can be used to determine genotypes of family members.
Can be used to help predict probability of future generations expressing certain traits.
Important tool for genetic counselors
Incomplete dominance – dominant & recessive traits are blended Example: Four o’clock
flower color – red, white, pink
Remember: Vegetable juice
Codominance – dominant & recessive traits both show up completely and individually Example: Blood types A &
B, Horse coat color Remember: Salad & cows
Multiple alleles - More than 2 alleles control the phenotype Example: blood types A, B, O, eye color
Polygenic traits – more than one gene controls phenotype Examples: skin (4
genes), fingerprints
Epistasis = one gene can interfere with the expression of another Examples: mouse
fur color (5 genes) – one gene overshadows the others
Albanism – no pigment
The environment can influence gene expression Affects phenotype
Examples: Sun exposure – affect s skin &
hair color Temperature – sea turtles
produce more females in warm years and more males in cold years
Identical twins – nutrition, healthcare & physical activity influence appearance
An individual’s fingerprints are controlled by polygenic inheritance, but also by the fetal environment. The ridge pattern of a fingerprint can be altered during weeks 6 – 13 of fetal development as the fetus touches the wall of the amniotic sac with its fingertips.
Identical twins who have identical genes have different fingerprints.
There are three alleles to blood Ai (antigen for A) Bi (antigen for B) Oi (antigen that
can be changed called H)
Ai produces the antigen A found on the RBC and co dominate
Bi, antigen B, co dominate
Oi, recessive changing antigen
Blood Type
Antigen
Antibodies Receives From
Donates To
A A, H Anti-B A, O A, AB
B B, H Anti – A B, O B, AB
AB A, B, H
none A, B, AB, O
AB
O H Anti-AAnti - B
O A, B, AB, O
Blood Typeof Parents
Possible Genotypesof Parents
Possible Blood TypesAmong Children
A and A Ai and Ai A and O
A and B Ai and Bi A, B, AB, O
A and AB Ai and AB A, B, and AB
A and O Ai and ii A and O
B and B Bi and Bi B and O
B and AB Bi and AB A, B, and AB
B and O Bi and ii B and O
AB and AB AB and AB A, B, and AB
AB and O AB and ii A and B
O and O ii and ii O
During mitosis, the 23 pairs of human chromosomes condense and are visible with a light microscope.
A karyotype analysis usually involves blocking cells in mitosis and staining the condensed chromosomes with Giemsa dye, “G”.
The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a dark band.
These bands are not a single gene but represent hundreds of genes.
analysis involves comparing chromosomes length the placement of
centromeres the location and
sizes of G-bands (stains)